Conventional power-driven impact tools, such as pneumatic hammers and boring tools, are spring-coupled to a surrounding hand grip assembly which has, on its upper end, a hand piece which is grasped by the tool operator. As is well known, unless suitable facilities are provided between the tool drive housing and the hand grip assembly, the strong vibratory forces generated by the tool via impact and shaking movements thereof are transmitted directly to the operator's body via the hand grip assembly. To avoid the obvious dangers thereof, various schemes have been proposed in the past to minimize the transmission of such vibrations.
In one suggested scheme, such vibrations are reduced by significantly increasing the mass of the hand grip assembly and/or providing a very soft spring between the tool drive housing and the hand grip assembly. Such construction, unfortunately, is too heavy and bulky for practical applications.
In another proposed scheme, suitable damping members are introduced in the mechanical circuit between the tool drive housing and the hand grip assembly. Such scheme has suffered from the fact that the introduction of such resistive damping itself sets up accompanying forces that prevent the attainment of the desired goal of isolating the hand grip assembly from the impact portion of the device.